Nature provides remarkable examples of microscale structures with complex three-dimensional (3-D) morphologies and finely-patterned features formed by living organisms. For example, intricate 3-D microscale silica or chitinous structures with organized nanoscale features are formed by diatoms (single celled algae) or Morpho butterflies, respectively. Synthetic rapid-prototyping or self-assembly approaches have also yielded 3-D structures with microscale and/or nanoscale particles/pores in certain desired arrangements. While such 3-D patterned structures can be attractive for particular applications, the materials readily formed by these processes may not possess preferred chemistries for a broader range of uses. The scalable fabrication of structures with complex 3-D morphologies and with a range of tailorable chemistries may be accomplished by separating the processes for structure formation and for chemical tailoring; that is, structures with a desired 3-D morphology may first be assembled in a readily-formed chemistry and then converted into a new functional chemistry via a morphology-preserving transformation process. In this presentation, several shape-preserving chemical conversion (conformal coating-based and fluid/solid reaction-based) approaches will be discussed for generating 3-D replicas of biogenic and synthetic structures comprised of ceramic, metal, or composite materials for catalytic, optical, energy harvesting/storage, and aerospace applications.

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